Re: [netmod] Deviations and augmentations

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Tue, 13 November 2018 18:26 UTC

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Date: Tue, 13 Nov 2018 19:26:21 +0100
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: Robert Wilton <rwilton@cisco.com>
CC: Andy Bierman <andy@yumaworks.com>, "netmod@ietf.org" <netmod@ietf.org>
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References: <a8c912c8-a7a5-1852-d053-10f0f11076e8@cisco.com> <20181112.173351.1984161388756642220.mbj@tail-f.com> <cbe0103b-112e-4687-e119-0698ea6cb9f4@cisco.com> <77b69d64-2ce2-29d9-77a9-04a7159003a9@ericsson.com> <CABCOCHQmA1PaVTu7oLiECXLrCULqW1KJddDRvYaDmE4xWu5AmA@mail.gmail.com> <98d6293c-d762-4d21-a9e2-c9cb20f74135@cisco.com> <CABCOCHR-vygv+Fq8JWGMm59-V6CB4PkqfSA_5mR8xBUqwi6xDw@mail.gmail.com> <453368b2-aa52-f09a-ea0b-960255bce46b@cisco.com> <20181113170652.intfq37w6rxyw4rq@anna.jacobs.jacobs-university.de> <c6de1ed9-7dfb-fff1-0069-fa22dc2e3303@cisco.com>
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Subject: Re: [netmod] Deviations and augmentations
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On Tue, Nov 13, 2018 at 05:54:27PM +0000, Robert Wilton wrote:
> 
> 
> I think that my main point regarding version numbers is:
> 
>  - If we are going to use semver then we should define and follow the rules
> strictly.  I.e. assuming that the semver has been populated correctly then
> it should be possible to determine whether the change is a nbc, bc, or
> editorial change.  I think that a solution where semver is done in a
> half-hearted way is entirely useless (e.g. if clients cannot trust the
> version number).  I think that there is a pretty clear requirement to
> support NBC changes to older revisions (i.e. I really mean bug fixes but a
> looser interpretation than your definition), and hence I don't think that
> vanilla semver is sufficient.

But even if you make the 'YANG world' use semvers correctly (not sure
how you want to achieve that but lets pretend you manage), then the
three digit number does not tell a client whether it will work or not.
What should a client do if semver indicate nbc? What should it do if
semver indicates bc? What should it do if semver indicates editorial
change? Where is the "protocol specification" for this?
 
> - An alternative is to not use a semver version number at all, instead we
> define a non semantic 3 digit version number that is something like:
> 
>  major = significant changes to the module have been made
>  minor = smaller changes/feature enhancements to the module have been made
>  patch = a bug fix to the module has been made.
> 
> Clients, module readers, etc, and then required to use a schema comparison
> tool to determine what the actual changes between two revisions are and
> whether or not they will be broken by those changes.

The only robust solution is schema comparison and we may think about
what kind of annotations make such schema comparisons easier or faster
or how we can help clients to adapt (e.g., providing pointers where
definitions have moved, providing machine readable information
allowing tools to track which modules replace others etc.).

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>